This undated photo released by the Los Angeles Police Department shows suspect Christopher Dorner, a former Los Angeles officer; The truck owned and driven by suspected cop killer Christopher Dorner during his alleged rampage through the Los Angeles area was found deserted and in flames on the side of Bear Mountain, Calif., Feb. 7, 2013.

The truck owned and driven by suspected cop killer Christopher Dorner during his alleged rampage through the Los Angeles area was found deserted and in flames on the side of Bear Mountain, Calif., this afternoon -- with tracks in the snow leading away from the vehicle.

The San Bernadino Sheriff's Department confirmed the truck was Dorner's, but said at a news conference this evening that the tracks around the truck did not lead to him.

Personnel from several departments and teams of dogs continued to search the area near Big Bear Lake, about 80 miles east of Los Angeles, including door-to-door searches of cabins located there, officials said.

Dorner, a former Los Angeles police officer and Navy reservist, remained on the loose.

"He could be anywhere, at this point, and that's why we're searching door to door," San Bernardino County Sheriff John McMahon said.

He added that the search would continue as long as it was possible. However, a snowstorm was forecast for the area.

Dorner was believed to have killed one police officer and injured two others early this morning in Riverside, Calif. He was also accused of killing two civilians on Sunday. And he allegedly released an angry "manifesto" airing grievances against police and warning of coming violence toward cops.

Heavily armed officers spent much of Thursday searching for signs of Dorner, investigating multiple false leads into his whereabouts and broadcasting his license plate and vehicle description across the California Highway System.

Around 12:45 p.m. PT, police responded to Bear Mountain, where two fires were reported, and set up a staging area in the parking lot of a ski resort. They did not immediately investigate the fires, but heavily armed SWAT team members eventually descended onto Bear Mountain from a helicopter manned with snipers to investigate and reached the truck.

Also today, CNN's Anderson Cooper said Dorner had sent him a package at his New York office that arrived on Feb. 1, though Cooper said he never knew about the package until today. It contained a DVD of court testimony, with a Post-It note signed by Dorner claiming, "I never lied! Here is my vindication."

It also contained a keepsake coin bearing the name of former Los Angeles Police Chief William J. Bratton that came wrapped in duct tape, Cooper said. The duct tape bore the note, "Thanks, but no thanks Will Bratton."

Bratton told Cooper on his program, "Anderson Cooper 360," that he believed he gave Dorner the coin as he was headed overseas for the Navy, Bratton's practice when officers got deployed abroad. Though a picture has surfaced of Bratton, in uniform, and Dorner, in fatigues, shaking hands, Bratton told Cooper he didn't recall Dorner or the meeting.

Police officers across Southern California were on the defensive today, scaling back their public exposure, no longer responding to "barking-dog calls" and donning tactical gear outdoors.

Police departments have stationed officers in tactical gear outside police departments, stopped answering low-level calls and pulled motorcycle patrols off the road in order to protect officers who might be targets of Dorner's alleged rampage.

"We've made certain modifications of our deployments, our deviations today, and I want to leave it at that, and also to our responses," said Chief Sergio Diaz of the police department in Riverside, Calif., where the officers were shot. "We are concentrating on calls for service that are of a high priority, threats to public safety, we're not going to go on barking dog calls today."

Sgt. Rudy Lopez of the Los Angeles Police Department said Dorner is "believed to be armed and extremely dangerous."

Early Thursday morning, before they believe he shot at any police officers, Dorner allegedly went to a yacht club near San Diego, where police say he attempted to steal a boat and flee to Mexico.

He aborted the attempted theft when the boat's propeller became entangled in a rope, law enforcement officials said. It was then that he is believed to have headed to Riverside, where he allegedly shot two police officers.

"He pointed a handgun at the victim [at the yacht club] and demanded the boat," said Lt. David Rohowits of the San Diego Police Department.

Police say the rifle marksman shot at four officers in two incidents overnight, hitting three of them: one in Corona, Calif., and the two in Riverside, Calif.

Lopez said two LAPD officers were in Corona on special detail to check on one of the individuals named in Dorner's manifesto and encountered Dorner. Dorner allegedly grazed one of them but missed the other.

"[This is an] extremely tense situation," Lopez said. "We call this a manhunt. We approach it cautiously because of the propensity of what has already happened."

After Dorner allegedly shot at LAPD officers in Corona, he fled and encountered two Riverside police officers stopped at a red light in their police car. Dorner used a rifle to shoot through their windshield, killing one officer and injuring the other, police said.

The deceased officer was a 34-year-old, 11-year veteran of the police department. The injured officer, age 27, was expected to make a full recovery.

Diaz said that the names of the officers were being withheld to protect their families, who might be targeted by Dorner if the names were released.

"They were on routine patrol stopped at a stop light when they were ambushed," Lt. Guy Toussant of the Riverside Police Department said.

In the manifesto Dorner published online, he threatened at least 12 people by name, along with their families.

"Your lack of ethics and conspiring to wrong a just individual are over. Suppressing the truth will leave to deadly consequences for you and your family," Dorner wrote in his manifesto.

A badge and identification belonging to Dorner have been found in San Diego, according to San Diego Police Sgt. Ray Battrick. Dorner's LAPD badge and ID were found by someone near the city's airport and turned in to police overnight, The Associated Press reported.

Los Angeles Police Department Chief Charlie Beck said today that 40 protective details have been deployed to protect officers and their families.

"We are taking all measures possible to ensure safety of our officers and their families," he said.

Lawrence was found slumped behind the wheel of his white Kia in the parking lot of their upscale apartment complex in Irvine, Calif., Sunday and Quan was in the passenger seat.

"A particular interest at this point in the investigation is a multi-page manifesto in which the suspect has implicated himself in the slayings," Maggard said.

Police said Dorner's manifesto included threats against members of the LAPD, and so the department is taking extra measures to ensure the safety of officers and their families.

The document, allegedly posted on an Internet message board this week, apparently blames Quan's father, retired LAPD Capt. Randy Quan, for his firing from the department.

One passage from the manifesto read, "I will bring unconventional and asymmetrical warfare to those in LAPD uniform whether on or off duty."

"I never had the opportunity to have a family of my own," it read. "I'm terminating yours."

Dorner was with the department from 2005 until 2008, when he was fired for making false statements.

Randy Quan, who became a lawyer in retirement, represented Dorner in front of the Board of Rights, a tribunal that ruled against Dorner at the time of his dismissal, LAPD Capt. William Hayes told The Associated Press Wednesday night.

According to documents from a court of appeals hearing in October 2011, Dorner was fired from the LAPD after he made a complaint against his field-training officer, saying in the course of an arrest she had kicked a suspect who was a schizophrenic with severe dementia.

After an investigation, Dorner was fired for making false statements.

"We have strong cause to believe Dorner is armed and dangerous," Maggard said.

Donner was also a Navy reservist who'd just finished his military career as a lieutenant on Friday. His only overseas deployment was to a Navy base in Bahrain. He also received a Rifle Marksman Ribbon and Pistol Expert Medal, meaning he received superior scores when he tested at the range.

Police described Dorner as black, 6-feet tall and weighing 270 pounds. He has black hair and brown eyes.

Meanwhile, Cal State-Fullerton was mourning the loss of its beloved assistant coach.

"There are really no words to convey the sadness that our program feels, that the young women who have had the privilege of working with such a bright and passionate woman," head coach Marcia Foster said earlier this week. "I want to especially send out condolences to Randal and Sylvia Quan, and her brother Ryan."

After college, Quan coached at Lutheran University in Thousand Oaks and has spent the past two years as an assistant coach at Cal State-Fullerton. The university has posted a memorial page on its sports website dedicated to Quan.

Lawrence was a business graduate who recently started working as a public-safety officer at USC.